Stability and Bioaccessibility of Carotenoids from Sea Buckthorn Pomace Encapsulated in Alginate Hydrogel Beads

Abstract

Carotenoids, the natural pigments that confer the bright orange color of sea buckthorn berries, are also associated with several health benefits, such as antioxidant activity and skin and eye protection. Due to their lipophilic nature and localization, carotenoids are largely retained in the sea buckthorn pomace (SBP) resulting from juice production. Carotenoids from SBP (70.03 mg/100 g DW), extracted and characterized by HPLC-PDA, contained zeaxanthin (free and esterified) and beta-carotene as major compounds. The SBP carotenoids-enriched sunflower oil was further encapsulated in Ca-alginate hydrogel beads (98.4% encapsulation efficiency) using ionotropic gelation. The hydrogel beads were characterized by confocal laser scanning microscopy and scanning electron microscopy. Fairly good stability (>64%) of the encapsulated carotenoids in the alginate hydrogel beads during storage (30 days, 4 °C and 25 °C) was found, with zeaxanthin esters being the most stable compounds, for all the experimental conditions. The bioaccessibility of the total carotenoids (INFOGEST protocol) was 42.1 ± 4.6% from hydrated, and, respectively, 40.8 ± 4% from dehydrated SBP alginate hydrogel beads. The addition of yogurt to the dehydrated hydrogel beads had a positive effect on the bioaccessibility of free and esterified zeaxanthin, but not on that of the carotenes. In conclusion, SBP is a valuable source of carotenoids which can be protected by encapsulation in alginate hydrogel beads, thus still retaining a good bioaccessibility.

Keywords: alginate hydrogel beads; bioaccessibility; sea buckthorn; stability; zeaxanthin.

Figure 1

HPLC-PDA chromatogram (λ = 450 nm) of carotenoids extracted from sea buckthorn pomace by UAE with MeTHF. Peak identification: 1—Zeaxanthin; 2—β-carotene; 3—γ-carotene; 4—Zeaxanthin-myristate-palmitate (ZMP); 5—Zeaxanthin dipalmitate (ZDP); 6—Lycopene.

Figure 2

A representative bright-field (A) and conventional fluorescence (B) image of the obtained alginate hydrogel beads dopped with SBP extract. The scale bar is 100 μm.

Figure 3

(a) Representative SEM image of the as-obtained alginate hydrogel beads. Inset represents microstructure and surface of alginate beads containing carotenoids. (b) Representative RCM-Vis image of an individual bead deposited onto a microscope glass.

Figure 4

Retention of total carotenoids from alginate hydrogel beads containing carotenoids from sea buckthorn powder during 30 days of storage in three different conditions: WRF—wet beads kept at refrigerator, WRT—wet beads kept at room temperature, and DRT—dehydrated beads kept at room temperature.

Figure 5

Bioaccessibility (%) of major carotenoids from alginate hydrogel beads containing sea buckthorn extract and subjected to in vitro digestion. (A) Bioaccessibility of xanthophylls; (B) Bioaccessibility of carotenes.